JP2005534369A - Apparatus and method for shock lead impedance measurement - Google Patents

Abstract

A device and method that automatically measures the lead impedance of a high energy shock lead prior to high energy therapy used to treat cardiac arrhythmia. In one example, the impedance measurement circuit measures the impedance between the electrodes of the plurality of electrode pairs. The measured lead electrode impedance is compared with a predetermined value to detect whether the lead is short-circuited with another lead. If the high energy shock electrode is shorted to another lead, the short lead indicator is set to a fault condition. Based on the status of the short lead indicator, the processor will discontinue or enable the high energy therapy. By checking for lead shorts prior to treatment, all of the treatment energy is delivered to the patient without being diverted by the shorted lead connections.

Description

  This document relates to pacemakers, defibrillators, and other devices capable of diagnosing and treating cardiac arrhythmias, especially to ensure effective shock treatment by automatically measuring shock lead impedance. It relates to an apparatus and a method.

  A pacemaker provides a timed continuous low energy electrical stimulus, called a pace pulse, to the heart via an intravascular lead (hereinafter “lead”) or the like. By sending pace pulses at an appropriate timing, the heart can be contracted with an accurate rhythm, and the pump efficiency can be greatly improved.

  A defibrillator is a device that can provide high energy electrical stimulation to the heart. Defibrillators can provide high energy electrical stimulation, also called defibrillation countershock. Counter-shock can stop fibrillation so that the heart can regain normal rhythm and pump blood efficiently.

  One problem that may arise is that the shock lead is disconnected and the shock electrode is shorted to the pacing lead or another shock lead. If a short circuit occurs, all the energy from the countershock is transferred to the inside of the device itself, not to the heart, and the device may be damaged. There is a need in the art to detect shorted leads.

  This document describes an apparatus and method for automatically measuring the lead impedance of a high energy shock lead prior to providing high energy therapy for use in treating cardiac arrhythmias. In one example, an impedance measurement circuit measures impedance between different electrode pairs. The measured lead electrode impedance is compared with a predetermined value to detect whether the lead is short-circuited with another lead. If the high energy shock electrode is shorted to another lead, the short lead indicator is set to a fault condition. Based on the status of the short lead indicator, the processor will discontinue or enable the high energy therapy. By checking for lead shorts prior to treatment, all of the treatment energy is delivered to the patient without being diverted by the shorted lead connections.

  In one example, the lead impedance is measured after the defibrillator or defibrillator / pacemaker device is charged in preparation for a countershock. If the shorted lead is not set to a fault condition and the lead impedance is greater than a predetermined value, shock therapy is continued. If the short lead indicator is set to a fault condition or the measured lead impedance is less than a predetermined value, shock therapy is discontinued.

  In another example, the lead impedance is measured while the device is being charged in preparation for a countershock. If charging is complete, the short lead indicator is not set to a fault condition, and the lead impedance is greater than a predetermined value, shock therapy continues. Treatment is also continued if charging is completed before the impedance measurement is completed and the short lead indicator is not set to a fault condition. If charging is complete and the short lead indicator is set or the lead impedance is below a predetermined value, the shock therapy is discontinued.

  This summary is intended to outline the subject matter of the present patent application and is not intended to be a limiting or exhaustive description of the invention. In order to provide further information about the subject matter of this patent application, a detailed description is added.

  In the following detailed description, references are made to the accompanying drawings that form a part hereof, and in which are shown by way of illustration specific embodiments in which the invention may be practiced. Other embodiments may be used and structural changes may be made without departing from the scope of the present invention.

  Overall, the various embodiments are described in the context of cardiac therapy performed by connecting electrodes to the coronary sinus (coronary arteriovenous) site, the right atrial site, and the right ventricular site and delivering shock treatment to the coronary sinus site. To do. However, the methods described herein may be modified to treat other types of cardiac arrhythmias by placing leads at other selected cardiac sites. In addition, the methods described herein may be adapted for unichamber therapy having multiple lead sites within a single chamber.

  FIG. 1 illustrates one embodiment of a portion of a system 100 for treating cardiac arrhythmias. The system 100 includes an implantable pulse generator (PG) 105 connected to a heart 120 of a patient 125 by a first cardiac lead 110 and a second cardiac lead 115, or one or more additional leads. The implantable pulse generator 105 can take the form of a pacemaker, defibrillator, or defibrillator that includes a pacing function. The system 100 also includes an external programmer 140 in preparation for wireless communication with the implantable pulse generator 105 using the telemetry device 145. The first cardiac lead 110 and the second cardiac lead 115 each include a proximal end and a distal end, and the distal ends of the leads 110, 115 are respectively a first heart site and a second heart site, Implanted in or on the heart 120. Each lead includes one or more electrodes that allow for a combination of monopolar and / or bipolar detection and energy transfer to the heart 120 for pacing and / or defibrillation. In some embodiments, the one or more electrodes include electrodes such as detection electrodes, pacing electrodes, shock electrodes, and the like.

  FIG. 2 is a schematic diagram illustrating one embodiment of a portion of the control circuit 200 of the implantable pulse generator 105 connected to the heart 120. As shown in FIG. 2, implantable pulse generator 105 includes a detection circuit 205 and a treatment circuit 220 connected to shock leads 110, 115. The implantable pulse generator 105 further includes a shock lead impedance measurement device 260, a power supply 270, and a control circuit / processor 225. In the illustrated embodiment, the control circuit / processor 225 includes the cardiac signal analyzer 230, the comparator 240, and the memory 250 to control the implantable pulse generator 105. In one embodiment, the functions of the analysis device 230 and the comparison device 240 are implemented in software within the control circuit / processor 225.

  The detection circuit 205 is connected to the implantable leads 110, 115. In some embodiments, the detection circuit 205 is connected to multiple leads. Each lead includes one or more shock / pacing electrodes and provides low / high energy therapy to the heart 120. The electrodes are placed at a number of selected heart sites of the heart 120, such as coronary sinus sites, ventricular sites, and superior vena cava sites. The electrodes connected to the leads 110 and 115 include a detection electrode, a pacing electrode, and / or a shock electrode. The detection circuit 205 receives a heart signal from the detection electrode and amplifies the received heart signal.

  The shock lead impedance measuring device 260 is connected to the electrode and measures the shock lead electrode impedance by measuring the impedance between each possible electrode pair including at least one shock electrode of all the arranged electrodes. To do. An example of a method for measuring defibrillation or shock lead impedance is to measure the voltage difference between a lead electrode and another electrode caused by a test current being sent through the lead to the other electrode. It is. The impedance is then determined by dividing the measured voltage by the test current. This method is described in US Pat. No. 6,317,628 to Linder et al., “Cardiac Rhythm Management System with Lead Impedance, which is fully incorporated herein by reference. Measurement System (a cardiac rhythm management system using a painless lead impedance measurement system) ”. Another example of a method for measuring defibrillation lead impedance is to calculate an impedance value from the voltage drop of a capacitively coupled output voltage pulse over a period of time. This method is disclosed in US Pat. No. H1,929 “Cardiac Rhythm Management System with Impedance Measurement (Cardiac Rhythm Management System Using Lead Impedance Measurement), fully incorporated herein by reference. "It is described in.

  Each possible electrode pair includes two or more shock electrodes, a shock electrode and a pacing electrode, a shock electrode and a detection electrode, a shock electrode and two or more pacing / detection electrodes, and a shock electrode and an implantable pulse generator 105. There is a conductive housing covering a part of the housing.

  A comparison device 240 connected to the shock lead impedance measurement device 260 compares each measured shock lead electrode impedance with a predetermined allowable shock lead electrode impedance value. In some embodiments, the predetermined allowable lead electrode impedance value is about 20 ohms.

  When the measured value of the lead electrode impedance is larger than a predetermined value, the analysis circuit 230 connected to the comparison device 240 can perform shock treatment through the lead. If the lead electrode impedance is less than or equal to a predetermined value, the lead is presumed to be in an electrically shorted state, and the analysis circuit 230 stops shock therapy using the lead.

  An electrically shorted state of the shock electrode occurs when one or more detached shock electrodes contact one or more placed sensing / pacing electrodes and one or more detached shock electrodes This is when it comes into contact with another placed shock electrode and the shock electrode has a bare coil.

  In some embodiments, analysis circuit 230 sets a short lead indication corresponding to the shock electrode based on the result of the lead impedance measurement. In some embodiments, the analysis circuit 230 sets one or more short lead indications for each shock electrode for which the measured shock lead electrode impedance is lower than a predetermined acceptable shock lead acceptance value. In some embodiments, the setting of the short lead indication includes the setting of a short lead flag. Setting the short lead indication may include writing one or more locations to the memory 250. In some embodiments, the shorted lead indication is cleared if the measured impedance value of the corresponding lead is greater than a predetermined value.

  In one embodiment, the first shock lead is connected to at least one shock electrode disposed about the coronary sinus site of the heart 120. The second shock lead is connected to a number of detection / pacing / shock electrodes placed around the right atrium of the heart 120. The third shock lead is connected to at least one pacing / shock electrode disposed around the superior vena cava site of the heart 120. The therapy circuit 220 is connected to the first electrode and provides high energy shock therapy to the coronary sinus site. In addition, treatment circuit 220 is connected to the second and third electrodes to provide low / high energy therapy to the right atrial and superior vena cava regions of heart 120.

  The treatment circuit 220 provides high energy treatment to the coronary sinus site using the first lead when the lead electrode impedance is greater than a predetermined value. If the shock lead placed in the coronary sinus part comes off and comes into contact with at least one of the other electrodes placed in the right atrial part or superior vena cava part, the measured lead electrode impedance falls below the specified value. Shock therapy is discontinued. The treatment is discontinued in order to maintain the integrity of the treatment circuit 220 and to ensure patient safety. In the present embodiment, based on the result of impedance measurement, the treatment circuit 220 performs low / high energy treatment on the right atrial region and the superior vena cava region. It is also envisioned that a shock lead is placed at the ventricular site of the heart 120.

  FIG. 3 is a flowchart illustrating one embodiment of a method 300 for providing shock therapy based on the results of lead electrode impedance measurements. At step 310, a detection lead placed in the atrium detects that shock therapy is being applied. In step 320, the shock lead electrode impedance is measured between each and every possible electrode pair including the shock electrode used to deliver the shock therapy. In some embodiments, the shock lead includes electrodes such as a pacing electrode and a sensing electrode. In some embodiments, electrodes are placed around a number of selected cardiac sites, including a coronary sinus site, a ventricular site, a superior vena cava site, and a conductive housing that covers a portion of the implantable pulse generator 105. The

  In step 330, the treatment circuit 220 is charged. When charging is complete, if short lead failure 340 is not displayed and a lead electrode impedance measurement 350 is made, then at step 360 each of the measured shock lead electrode impedances is a predetermined shock current. It is compared with the lead electrode impedance value. If the lead electrode impedance is greater than the predetermined value, shock therapy is continued at step 370. In one embodiment, the predetermined shock lead electrode impedance value is about 20 ohms.

  If the charge 330 is complete, the short lead failure 340 is not displayed and the lead electrode impedance measurement has not been taken 350 or has not been completed, at step 370, shock therapy continues.

  If charging is complete 330, a short lead failure 340 is displayed, or a lead electrode impedance measurement is performed 350 and the measured lead electrode impedance is less than or equal to a predetermined shock lead electrode impedance value, step 375 Thus, the short lead indicator is set to a fault condition and at step 380 the shock therapy is stopped. However, arrhythmia therapy continues 385 as if shock therapy had been administered. In some embodiments, the occurrence of an event that shock therapy was discontinued is recorded. When the number of recorded events reaches a predetermined number, no further shock treatment can be given. In one embodiment, the number of events recorded is six.

  In one embodiment, the shorted lead flag is cleared when the shorted lead is repaired. Generally, the flag is cleared by a doctor or a trained medical worker.

  FIG. 4 is an alternative to the method shown in FIG. In this embodiment, the lead impedance is measured at step 420 and the failure of the shorted lead is confirmed at step 440 without charging the treatment circuit 220.

  FIG. 5 is a flowchart illustrating another embodiment of a method 500 for delivering shock therapy based on the results of lead electrode impedance measurements. In step 510, it is determined that shock therapy is to be administered. At step 520, the shock lead impedance is measured between all possible electrode pairs, including the shock electrode used to deliver the shock therapy, while the therapy circuit 220 is charged. If charging is complete 530, no shorted lead failure is displayed 540, lead electrode impedance measurement is completed 550, and the lead electrode impedance value is greater than a predetermined impedance value 555, step 565 continues shock therapy. Is done. In one embodiment, the predetermined shock lead electrode impedance value is about 20 ohms.

  If charging is complete 530, no shorted lead failure is displayed 540, and lead electrode impedance measurement is not completed 550, lead electrode impedance measurement is stopped at step 560 and shock therapy continues at step 565. Is done.

  If charging is complete 530, a short lead failure is indicated 540, or if lead electrode impedance measurement is complete and the lead electrode impedance is less than or equal to a predetermined value, at step 570, shock therapy is discontinued and step 575. The short lead indicator is set to a fault condition. However, arrhythmia therapy is continued 580 as if shock therapy was being applied. In some embodiments, continuing as if shock therapy is being administered includes recording the occurrence of an event that shock therapy has been discontinued. When the number of recorded events reaches a predetermined number, no further shock treatment can be given.

  Although specific examples have been illustrated and described herein, those skilled in the art will appreciate that other embodiments possible to accomplish the same purpose may be used in place of the specific examples shown. will do. This application includes modifications or variations of the present invention. Accordingly, the invention is limited only by the claims and the equivalents thereof.

1 is an overall view showing one embodiment of a portion of a system for treating cardiac arrhythmias and the environment in which the system is used. 1 is a block diagram illustrating a portion of an apparatus for treating cardiac arrhythmias connected to a heart. FIG. 6 is a flowchart illustrating one embodiment of a method for performing shock therapy based on the results of lead impedance measurements. 6 is a flowchart illustrating another embodiment of a method for performing shock therapy based on the results of lead impedance measurements. 6 is a flowchart illustrating another embodiment of a method for performing shock therapy based on the results of lead impedance measurements.

Claims (19)

A plurality of implantable leads including at least one high energy shock lead and including at least one electrode;
An impedance measurement circuit connected to the plurality of electrodes so as to measure the impedance between the electrodes of the plurality of electrode pairs;
A control circuit connected to the impedance measuring circuit, wherein when the impedance between the electrode pairs is smaller than a predetermined value, the short-circuit lead indicator is set to a failure state, and the short-circuit lead indicator is set to a failure state. An implantable device for treating cardiac arrhythmia, comprising a control circuit that ceases therapy when being done.   The apparatus of claim 1, wherein the impedance measurement circuit measures impedance between electrodes of a plurality of electrode pairs, each having at least one shock electrode.   The control circuit sets the one or more short lead indicators associated with each of the shock electrodes to a fault condition when the measured impedance between electrode pairs is less than or equal to a predetermined value. The device described.   When the measured impedance between the electrode pairs is greater than a predetermined value, a processor connected to the impedance measuring device indicates the fault condition of one or more short-circuit lead indicators associated with each of the shock electrodes. The device of claim 3, which clears.   The apparatus of claim 4, wherein the predetermined value is about 20 ohms.   The at least one implantable lead and lead electrode are configured to detect cardiac signals generated at at least one heart site, including a coronary sinus site, a superior vena cava site, and a right ventricular site. apparatus. Determining that there is a condition for shock treatment;
Measuring the impedance of the shock electrode to at least one other electrode;
Applying the shock therapy when the impedance to the at least one other electrode is greater than a predetermined value;
Stopping the shock treatment when the electrode impedance is less than or equal to a predetermined value.   The method of claim 7, wherein the shorted lead indicator is set to a fault condition when the electrode impedance is less than or equal to a predetermined value.   The apparatus of claim 7, wherein the predetermined value is about 20 ohms.   8. The method of claim 7, wherein measuring the impedance of the shock electrode comprises measuring the impedance between the electrodes of the plurality of electrode pairs, each having at least one shock electrode.   11. The apparatus of claim 10, wherein the electrode pair includes at least one electrode adapted and configured for use at at least one heart site, including a coronary sinus site, a superior vena cava site, and a right ventricular site. The step of stopping the shock treatment is
Continuing the arrhythmia treatment algorithm as if shock treatment had been applied;
Recording the event as being treated;
8. The apparatus of claim 7, further comprising the step of discontinuing shock therapy when a predetermined number of recorded events have been received. Determining that there is a condition for shock treatment;
Measuring the impedance of the shock lead electrode while the shock therapy device is being charged;
Charging the shock therapy device, completing the electrode impedance measurement, and performing the shock therapy when the measured electrode impedance is greater than a predetermined value;
If the charging of the shock treatment device is completed, but the electrode impedance measurement is not completed, stopping the electrode impedance measurement;
Continuing the shock treatment when the shock treatment device is fully charged and the electrode impedance measurement is discontinued;
A method of performing shock therapy, comprising: charging the shock therapy apparatus, completing the lead impedance measurement, and stopping the shock therapy when the electrode impedance is equal to or lower than a predetermined value.   14. The method of claim 13, comprising setting the shorted lead indicator to a fault condition when the electrode impedance is less than or equal to a predetermined value. Applying the shock therapy if the short circuit lead indicator is not set to a fault condition; and
Continuing the shock treatment when charging of the shock treatment device is complete, the electrode impedance measurement is stopped, and the shorted lead indicator is not set to a fault condition;
15. The method of claim 14, comprising discontinuing the shock therapy if the short circuit lead indicator is set to a fault condition.   The method of claim 14, wherein the predetermined impedance value is about 20 ohms.   The method of claim 13, wherein measuring the impedance of the shock electrode comprises measuring the impedance between the electrodes of the plurality of electrode pairs, each having at least one shock electrode.   18. The method of claim 17, wherein the electrode pair comprises electrodes adapted for use at a coronary sinus site, a superior vena cava site, and a right ventricular site of the heart. The step of discontinuing shock treatment is
Continuing the arrhythmia treatment algorithm as if shock treatment had been applied;
Recording the event as being treated;
14. The method of claim 13, further comprising the step of discontinuing shock therapy when a predetermined number of records of treatment has been administered.

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